Manual control mechanism



June 27, 1950 v F|$HER I 2,512,770

MANUAL CONTROL MECHANISM Filed Nov. 24, 1944 INYVENTW? Patented June 27,1950 UNITED STATES PATENT OFFICE 2,512,770 MANUAL CONTROL MECHANISMApplication November 24, 1944, Serial No. 564,976

My invention relates to an improvement in regulating apparatus of theclass in which a member is automatically positioned in response to apreexisting condition, but which has optional means for manual control.In particular, the invention applies to a means for indicating theposition of a remote member during the period when said member issubject to manual control. The present invention is an improvement forthemechanism disclosed in the co-pending application of John M. Wilson,Serial No. 461,970, filed October 14, 1942, now Patent Number 2,397,068,issued March 19, 1946.

In the co-pending application referred to above, an automaticallycontrolled planetary gear mechanism is provided for controlling theposition of a heat control valve for an aircraft cabin. Provision ismade for manuallypositioning said valve control member in the event thatan alternative condition is desired, or, in the event of failure of thepower controlled motor means. The present invention is provided forindicating the position of said valve control member during the periodof manual control, which position cannot otherwise be indicated becauseof the nature of the automatic portion of the control mechanism.

In the present invention, a movable member having an index shield isarranged to be mounted adjacent the manually controlled portion of thedevice and is so arranged as to be made movable by the manuallycontrolledmember if necessary, and when properly positioned, it willindicate the range of movement required by the manualmemher to positionthe valve control member any- Where between open and. closed. positions,thereby enabling the operator to select a desired position of the valve.

The principal object of my invention is to provide means cooper-ablewith a planetarymechanism having optional manual control, for indicatingthe position. of the controlledmember during the period of manualcontrol.

Other and further objects will. become apparent in the following.description and claims, and in the appended drawings inv which:

Figure I is a showing of the complete system with certain parts brokenaway, and others in 10 Claims. (01. 116-124.

Referring to Figures 1 and 3, the planetary mechanism comprises asubstantially circular plate I'll having an arm H extending therefrom.The plate Ill and arm ll constitute the devicezor member which is to bepositioned, or the driven arm of the apparatus. This driven arm H may beutilized to control any desired apparatus and it is herein contemplatedthat'the arm H willbe connected to any suitable heat control mechanism,such as for use in heating the cabin of an aircraft. Three stud shafts,l2, l3, and M are secured to the plate H! at equally spaced points on animaginary circle having the same center as the periphery of the circularplate I0. Mounted upon the stud shafts t2, I3, and M for rotationcross-section to more clearly show the structure are planetpinio'ns l5,l6, and H. The stud shafts l2, l3, and I l extend entirely through theplanet pinions I5, l6, and I1, and through a plate i-"8 which serves tosecure the front end of the stud shafts I2, I3, and M as viewed'inFigure 1. Also located between theplates l0 and i8 and meshing with eachof the planet pinions l5, I6, and I1 is a sun pinion IS. The sun pinion19 is secured to atubular bearing member 20 which extends through theplate It and terminates at some distance inside of it. The interior ofthis tubular bearing member 20 is secured to a final driven shaft 2|which is connected to a reversible electrio motor 22 of the split-phasetype through a suitable reducing gear train 23. The tubular member 20may be secured to the shaft M in any desired manner and is herein shownas keyed thereto at 24. Cooperating with the outer portions of eachofthe planet pinions l5, l6, and I1 is an internal gear 25. This internalgear 25 may be made integral with, or be fixedly secured to a cable drum2B.

The cable drum 26' may of itself constitute the manual operator.However, it is preferred to have the manual operator capable of beinglocated at a point remote from the planetary mechanism. To accomplishthis purpose, a remote manual operator is connected to the cable drum26. Re-

ferring now to the upper part of Figure 1 and to Figure 2, the remotemanual mechanism includes a mountingplate 30 having mounting holes 31therein by means of which the plate 30 may be secured to any desiredpart of the aircraft cabin so that the manual operating means can beconveniently operated by the pilot. The lower half of the mounting plate30 is substantially rectangular in formwhere'as the upper half thereofis in-the form of asemicircle having teeth or notches 32 formed in theperiphery thereof. Extending backwardly from the mountingplate 30 is atrunnion shaft 33 upon which a second cable drum i mounted. This cabledrum comprises the drum portion proper 34, and the bearing member or hub3'5 which rotates upon the trunnion 33. This hub 5 is retained on thetrunnion 33 in any suitable manner such as by the cotter pin 35.

A plate 32' is secured to the cabledrum 34 by means of screws 38. Formedintegrally with the plate 3l'is a cylindrical housing 39 provided withan internal bore 48. Closely fitting and slidably mounted within thebore 40 is a cylindrical memher 4!, and a notch portion 42 adaptedtoengage the notches formed by the teeth 32 on the semi-circular portionof plate 38. Formed integrally with the cylindrical member 4i and eX-tending upwardly therefrom is a shank 43 terminating in a screw threadedportion 44 to which an operating knob 45 is secured by means of a nut46. 40 having its upper end bearing against the underside of the housing39 and its lower end bear- "111g against the upper side of thecylindrical member 4!, whereby the latching portion 42 is biaseddownwardly. As a result, the cable drum 34 is normally latched in astationary position. 1

The position in which the cable drum 34 is shown latched in Figure l isthe automatic position as indicated on the plate 30 and as will bedescribed hereinafter.

When it is desired to rotate the cable drum 34 in either direction, theoperating knob 45 is pulled upwardly against the bias of spring 41 so asto remove the latching portion 42 from one of the notches between theteeth 32. Then, while the operating knob 45 is so held in an upwardposition, the Whole assembly including the cable drum 34 may be rotatedin either direction through substantially a quarter of a turn. If it 'isthen desired to lock the cable drum 34 in some new position, the manualoperating knob 45 is released whereupon the latching portion 42 entersa'different notch between the teeth 32, and

the drum 34, is thus locked in its new position. A pin 48 extendshorizontally from the cylindrical member 4! through a notch 49 in thehousing.

' 39 to prevent turning of the latching portion 42 -'so that it cannotbecome crosswise in the teeth 32.

Forreasons which will appear hereinafter, it is desirable to break anelectrical circuit upon movement of the cable drum 34 out of itsautomatic position in which it is shown. To accomplish this, a snapswitch 50 having terminals 5i and 52 is secured to the mounting plate 30by means of screws 53. The snap switch 50 has a cylindrical extension 54which extends through a suit-able opening in the mounting plate 30. Thesnap switch 50 further includes an operating pin or push button 55 whichextends through and projects beyond the cylindrical portion 54. A switchactuating member 5b having a push button operating portion 57 is securedto the cable drum 34 in such a position that it is engaged with the pushbutton 55 and holds it in its innermost position when the cable drum 34is in the automatic position as shown in Figure 1. However, upon slightmovement of the cable drum in either direction away from the automaticposition, the-push button actuating extension 5'! will move out fromunder the push button 55 whereupon the push button 55 auto- .matically,through a biasing means contained within the switch 56, moves to itsouter position. The switch 50 may be of any suitable type wherein acircuit is opened whenever the push button is in its outer position towhich it is biased andv in which such circuit is closed when the push Aspring 4'! is mounted within the bore button is held in its innermostposition as it is with the parts in position shown in Figures 1 and 2.This switch 50 may take the form disclosed in Patent 2,318,734 issued toAlbert E. Baak, on May 11, 1943.

The cable drums S4 and 26 are interconnected by means of a. cable 60. IFor this purpose the cable drum 34 is provided with a slot 6! and acable clamping plate 52 which can be held in clamping position by meansof a screw 63. One end of the cable is clamped by means of a. clampingplate 82. The cable is then wound about the 7 cable drum 34 forsubstantially a complete turn after which it is Wound completely aroundthe cable drum 26 and then is again wound about the cable drum 34 thegreater portion of a turn and the second end is then clamped by theclamping member E32. In order to prevent slippage of the cable on thecable .,drum 25, the cable drum is provided with a pair of slots 64 anda pin 55. When the cable is wound about the drum 26, it is brought outof one of the slots 54, wound around the pin and then out through theother slot 64, and then wound around the pin 65 and then passes throughthe other slot 54 back onto the cable drum 26.

In the foregoing arrangement it will be seen that the cable drum 34 willbe held stationary by means of the latching mechanism and through thecable 68. The cable drum 26 to which the internal gear 25 is securedwill also be held stationary. However, the cable drum 34 may be r0 tatedto a limited extent in each direction away from the automatic positionby means of the housing 39 and such rotative movement will betransmitted to the cable drum 26, to provide manual means for rotativelymoving the operating arm H. The mechanism has been so constructed thatthe operating arm or driven member H is capable of arcuate movementthrough degrees. Stop members, one of which is shown as'lla are providedat the opposite extremes of movement of the arm Ii to limit the arcuatemovement of the driven member. The cable drum 34, which is intended toprovide manual means of moving the arm i l through connection with cabledrum 26, is made sufficiently larger than cable drum 26 so that 75degrees of rotation in either direction of cable drum 34 will besufiicient to move cable drum 2% and arm ii, 120 degrees because of therelative sizes of these two drums.

The power means'constituting the split-phase motor 22 may be controlledin any desired manner. There is herein disclosed an automatic controlsystem of the temperature responsive type which includes a resistancebridge circuit iii and an electronic amplifier H. The bridge circuit 19includes in one arm a temperature responsive resistance T2 of usualconstruction, the resistance of which increases upon temperature rise.This temperature resistance 52 may respond, for example, to thetemperature in an aircraft cabin. The

three other arms of the bridge circuit include fixed resistances 13, I4,and 75. Those arms which include the fixed resistances l4 and "i5,additionally include a variable amount of resistance of a balancing orfollow-up potentiometer. This potentiometer includes a balancingresistance '16, the left-hand end of which is connected to the lower endof the fixed resistance 75, by

a wire 11, whereas its right-hand end is connected to the lower end offixed resistance 14 by a wire 18. The balancing resistance l6 may besuitably carried by a housing 19 so that it is stationary and doesnotmove. Cooperating with this balancing resistance 18 is a slider arm 88which moves in accordance with'the movement of the plate II] or drivenarm II. 'For :convenience, the slider arm '88 has therefore :been shownas attached to the plate 18 through a piece of insulating material 8|.In actual practice, the motor 22, gear train 23, and the planetarymechanism may be conveniently mounted in the housing generally indicatedby the dotted line 19.

The electronic amplifier ll includes a pair of terminals '82 and 83 forsupplying power to the bridge 10. Terminal 82 is connected'to abridgeinput terminal (Why a wire 85. The'bridge input terminal 84 comprisesthe junction of those arms which include the temperature sensitiveresistance l2 and the fixed resistances 15. Similarly, amplifierterminal 83 is connected 'to a bridge input terminal 86 by a wire 81.The bridge input terminal 86 comprises the junction of those arms of thebridge which include the fixed resistances 13 and M. The amplifier 1|further includes a pair of amplifier input terminals 88 and 89. TerminalB8 is connected to a bridge output terminal 98 by means of 'a wire 9|.This terminals!) constitutes the junction of those arms of the bridgecircuit which includethe temperature sensitive resistance 12 and thefixed resistance 13. The other terminal 89-of the amplifier is connectedto slider arm '80 by means of a wire '92. In addition, the electronicamplifier H includes a pair of incoming power terminals 93 and 94. Powerterminal 93 is directly connected to one wire '95 of any suitable sourceof alternating current. means of wire 96 to the terminal '52 and switch50. .The terminal thereof is connected to the otherwire '91 of thealternating source of power.

The resistance bridge 18, the electronic amplifier II, and the mannerin'wh'ich they are interconnected may take any of the forms shown in theart, but preferably utilize a system of the type disclosed in theco-pending application of Albert P. Upton, Serial No. 437,561, filedApril '3, 1942, now Patent Number issued July 8, 1947. In the type ofsystem disclosed in the said Upton application, the split-phase motor'22 is provided with the 'usual two windings, one of which is constantlyenergized, and the other being energized only when the bridge circult isunbalanced. However, upon unbalance of the bridge circuit in onedirection, the second winding of the split-phase motor is energized witha current which has a phase leading that of the constantly energizedwinding-whereupon the motor rotates in one direction. (3n theother hand,when the bridge is unbalanced in the opposite direction, the secondwinding of the splitphase motor is supplied with a current which has aphase which lags that of the constantly energized winding with theresult that the motor rotates .in the opposite direction.

A sector I98 is mounted on a trunnion shaft llll which extends forwardlyfrom the plate 3H. Ihe sector is frictionally supported on the shaft HMbetween the frictional washers I02 and 103 by a tension spring 104 whichis heldxby a nut 405 that is threaded onto the end of the shaft .HH. Anarcuate portion H16 of the sector is provided with an index shield whichindicates the relative position of the driven member or :as in thiscase, the position of the valve which is in turn controlled by thedriven member. Orr-each end of the arcuate portion I116 are opposingprojections I01 and I08 which are provided-120 0001 Terminal 94 isconnected by B erate with afinger 109 that extends downwardly fromthetforward edge of the latching housing 39. The purpose of thefrictionally mounted segment and the projection I09 are to provide ameans for indicating the position of the driven member ll :ortthe valvewhich it controls. It will .be remembered that the movement of cabledrum 34 by the latch housing 39 in either direction for 75 degreesprovides movement of the driven arm 120 degrees, therefore this deviceserves to inform the pilot or operator, of the position of the drivenmember during the-period of manual operation, regardless of the positionit had assumed at the time of changeoverfrom automatic to manualcontrol, which position could not 0therwise be detected, since thedriven member is remotely located from the manual station.

Automatic operation With the parts in the positions shown, the manualoperator is in the automatic position with the result that the pushbutton v55 of the switch 59 is in its "innermost position and a circuitis closed between the terminals 5| and 52 of the switch 50. Therefore,power is being supplied to the electronic amplifier H. Also, with theparts in the position shown, the temperature of the aircraft cabin is atan intermediate value and the heat control or valve operating arm H isin a position intermediate its possible extreme positions. Similarly,the slider arm is on the center of the balancing resistance 16. Undersuch conditions, the bridge 18 is in balance and the v.secondwincling ofthe split-phase motor .22 is deenergized so that the motor isstationary.

Now let .us assume that the temperature in the aircraft cabin rises.Under .such condition, the resistance of the temperature sensitiveresistance 12 increases and the bridge 78 is unbalanced. As a result,the electronic amplifier T-I supplies the second winding of the splitphase motor 22 with a current out of phase with that of the constantlyenergized winding. and in such direction that the sun pinion I9 isdriven in a clockwise direction. Since the internal gear 25 is beingheld stationary by the remotely located manual mechanism, the planetpinions I5, I6, and I! in rotating in a counterclockwise direction abouttheir respective stud shafts l2, l3, and M, will cause the plate I 6upon which the stud shafts are mounted to rotate in a clockwisedirection. This operation will cause the arm H to move in a clockwisedirection so as to move the valve or heat control apparatus towardclosed position to reduce the amount of heat applied to the aircraftcabin. Such movement of the plate I!) causes theoouter arm 36 to movetoward the right-hand ,end of the balancing resistant 16. Whensufllcient movement has taken place, the bridge circuit will beunbalanced. When this occurs, the electrenic amplifier H will deenergizethe .second winding of the split-phase motor 22 whereupon the rotationof the sun pinion is will cease. Likewise, the plate ill will cease itsmovement,

On the other hand, if the temperature within the aircraft cabin shouldfall, the resistance of temperature resistance l2 decreases. Thisunbalances the bridge 18 in the opposite direction, causing theelectronic amplifier H to energize the second winding of. motor v22 witha current having an opposite phase than occurred. upon temperature rise,so that the sun pinion i9 isrotated in a counterclockwise direction.Inasmuch as the internal gear 25 isstill-being held vst'ationary, thiscounterclockwise rotation of the sunpinion I9 results incounterclockwise rotation of 'plate I!) and control arm II, causing theheat control valve to move toward open position to supply additionalheat to the cabin and at the same time to cause slider arm 80 to move 1toward the left-hand end of balanced resistant I6. When sufficientcounterclockwise movement of the control arm H and the slider arm 80 hastaken place, the bridge Ii! will be rebalanced, whereupon the electronicamplifier H will deenergize the second winding of the motor 22 andfurther counterclockwise rotation of the sun pinion I9 will cease.Likewise, the plat I and the accompanying parts will also cease theirmovement.

In this manner, as long as the manual operator is in the automaticposition, so that the internal gear 25 is held stationary, the arm IIwill be positioned in accordance with the movement of motor 22 which inthis end are in accordance with the temperature fluctuation at thetemperature sensitive resistance I2 which responds to the temperature ofthe interior of the aircraft.

Manual operation It may be desired to take over manual positioning ofthe arm I I :at certain times. This manual positioning may be desiredwhen the electrical system is in operative condition or it may bedesired when for some reason or other the electrical system isinoperative.

Let us assume it is desired to increase the temperature of the aircraftcabin manually. The instant position of the valve or the valve controlarm I I is unknown to the pilot or operator since this portion of thedevice is remote from the cabin; however, for example, let us assumethat it is in the vertical mid-position shown in the lower portion ofFigure l, which is indicative of a half-opened position of the valve.The position of the sector ififl at this time is not indicative of theposition of the arm l I but when manual control is assumed, the scaleI06 should indicate the instant position of arm H. Therefore, tocoordinate the positions of arm II and sector I00, it may be necessaryto move the knob 45 and control housing 39 in either or both directionsto obtain this result. If the sector were in the position shown in theupper portion of Figure 1 and the housing 39 were moved in acounterclockwise direction to move the arm I I to a fully open position,the pointer H19 would indicate on the scale I that the position wasslightl less than half open, which of course is not the true position ofthe arm I I. Therefore to properly position both the arm H and sectorii"), the knob 45 is lifted so as to disengage member 42 from the gearteeth 32 and the housing is moved in a clockwise direction as far as itwill go. This operation will cause the arm I l to move to a fully closedposition and the pointer I99 will engage projection I88 and move thesegment 180 in a clockwise direction so that when the housing 39 hasreached the limit of its clockwise movement, pointer I89 will indicateon scale I06, that the valve is fully closed.

Then by moving the housing 38 in a counterclockwise direction, the arm II will move towards open position and its actual position will beindicated on scale I 66, and if the housing 39 is moved over its fullrange of movement to open position, pointer I99 will be in engagementwith projection I81, which on scale it indicates a fully open positionof the valve. Movement of the manual operator causes the switchactuating member 51 to move away from the push button 55, whereupon thebutton moves outwardly and breaks the circuit between terminals 5| and52 of the switch 56.; Breaking of this circuit interrupts the powersupplied to the electronic amplifier II so that the motor 22 remainsstationary irrespective of whether or not the electrical circuit isotherwise in operative condition. The movement of the manual operator istransmitted through cable 60 to the cable drum 26 and the associatedinternal gear 25 which likewise moves in the same direction. At thistime, the sun pinion I9 is stationary because the motor circuit isbroken, so that the motion of the internal gear results in the movementof plate II! and the driven arm II, which causes opening or closing ofthe heat control valve to thereby supply more or less heat to theaircraft cabin. Since it was previously assumed that the operating armII was in the mid-position, the manual member could only be movedthrough an arc of 37 degrees or M; of the toothed area of the plate 30to bring the operating arm I I against the stop member I la whichrepresents a full open position of the valve controlling member. Had thevalve member been in a closed position, it would have been necessary tohave moved the operating member through an arc of degrees in acounterclockwise direction, or had the valve been in a full openposition at the time manual control was assumed, the manual member couldnot have been moved at all in a counterclockwise direction. Thus it willbe seen that if the manual member is moved to the full allowable extent,th frictionally mounted sector I00 will indicate this as a full openposition of the valve and thereafter the pilot or operator may retractthe manual member to a position indicated on the index shield portionI06 which will represent a fractional opening of the valve.

Thus, it will be understood that the purpose of the present invention isto provide a simple and inexpensive means of indicating the position ofthe driven arm or the valve member at any time after manual control ofthe system has been assumed :and that this modification is meritoriousin that otherwise the pilot or operator is not aware of the position towhich the manual member must be moved in order to obtain a measuredresponse from the driven member or heat control valve.

It will be obvious in its broader aspects, that it is immaterial as tothe type of power means used or the manner in which it is controlled. Itwill likewise be obvious that other changes may be made in my inventionwithout departing from the spirit thereof, and I therefore intend to belimited only by the scope of the claims appended hereto.

I claim as my invention:

1. In a mechanism for positioning a driven member having a drivingmechanism with a manually operable portion which when operative has asubstantially greater range of movement than the range of movement ofsaid driven member, a movable member associated with said manuallyoperableportion which is movable by an element of said manually operableportion to indicate one extreme position of said driven member and therange of movement required of said element to move said driven member toits opposite extreme position.

2. In a planetary mechanism for controlling a driven member, having anautomatically controlled planet mechanism for normally control- 75 lingsaid driven member and a manually operated motor operated portion forautomatically positioning said control member and: a manually operableportion adapted to supersede said motor operated portion while saidmotor operated portion is held stationary having a manually movablemember, a member for indicating the position of said control memberduring the period of manual control, said indicating member beingfrictionally mounted on said manually operable portion, and saidindicating member having a projection engageable by said manuallymovable member whereby said manually movable member is adapted to movesaid indicating member to a position representing an extreme position ofsaid control member after which said manually movable member may beindependently positioned adjacent a point on said indicating memberrepresenting a position of said control member.

4. A dual control mechanism for positioning a control member, comprisingin combination, a motor operated portion for automatically positioningsaid control member and a manually operable portion adapted to supersedesaid motor operated portion while said motor operated portion is heldstationary having a manually movable member, a movable indicating memberfor indicating the position of said control member during the period ofmanual control, and said indicating member having opposed projectionsengageable by said manually movable member and being movable thereby toa position where one of said projections represents one extreme positionof said control member and the opposite projection represents the otherextreme position of said control member.

5. In a device of the class described, a driven member, a manuallyoperable member for moving said driven member, a planetary gearmechanism for transmitting movement from said manually operable memberto said driven member, said manually operable member being movablethrough an arcuate course, and a movable sector associated with saidmanually operable member for indicating the position of said. drivenmember, said sector being movable relative to said manually operablemember but being so disposed with relation to said manually operablemember as to be movably controlled thereby.

6. In a device of the class described, a driven member, a manuallyoperable driving member for moving said driven member, a planetary gearmechanism for transmitting movement from said manually operable memberto said driven member, said manually operable member being movablethrough an arcuate course, a movable sector associated with saidmanually operable member for indicating a relative position of saiddriven member, said sector being movable relative to said manual memberbut disposed with relation to said manual member as to be movablethereby, and means for locking said manual member in a selected positionwith respect to said-sector, rep"- re's'enting a selected position" ofsaid driven member. 1

7.- In apparatus of the class described, a driven member, motor operatedmeans for positioning said member, afined support means, a; manuallyadjustable member moveably attached to said support means, anindicatingmeans moveably attached to said support means, latchin means for lockingsaid. manual-1y: adjustable member to said support means, means forrendering said motor operated. means immovable, mechanical meansconnected to said manually adjustable member for engaging and movingsaid indicating means to an extreme position when said manuallyadjustable member is adjusted to an extreme position, means operativelyconnecting said manually adjustable member to said driven member, anddrive means for causing operation of said driven member by said motormeans when said manual means is locked and for causing operation of saiddriven member by said manual means when said motor operated means isimmoveable.

8. In apparatus of the class described, a driven member moveable througha predetermined range, a support means, a manually adjustable membermoveably attached to said support means, latching means for holding saidadjustable member in any one of a plurality of positions relative tosaid support means, mechanical means connecting said adjustable memberto said driven member in such manner that full movement of saidadjustable member either way from one of said positions may effect fulladjustment of said driven member, and indicating means attached to saidsupport means and having a lost motion connection with said manuallyadjustable member of such extent that said manually adjustable membermay be moved an amount required to move said driven member through itsrange without causing movement of said indicating means but so thatadditional movement may then cause movement of said indicating means.

9. In apparatus of the class described, a driven member moveable apredetermined extent, a support means, manually adjustable meanspivotally mounted on said support means and movable to any of aplurality of positions, motiontransmitting means connecting saidadjustable means to said driven member, said motion transmitting meansbeing arranged so that said driven member may be operated through itspredetermined extent by operation of said manually adjustable means ineither direction from one of said positions, an indicating meanspivotally mounted on said support means and having projections spacedapart an angular amount substantially corresponding to the angularmovement of said manually adjustable means required for adjusting saiddriven means through said predetermined extent, and a projecting memberconnected to said manually adjustable means engageable with one or theother of said spaced projections.

10. In apparatus of the class described, a driven member moveable apredetermined extent, a'

arranged so that said driven member may be operated through itspredetermined extent by operation of said manually adjustable means ineither direction from said position, an indicating means pivotallymounted on said support means and having projections spaced apart anangular amount substantially corresponding to the angular movement ofsaid manually adjustable means required for adjusting said driven meansthrough said predetermined extent, spring means for urging saidindicating means in frictional engagement with said support means, and amember projecting from said manually adjustable means engageable withone or the other of said spaced projections.

GEORGE H. FISI-ER.

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